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config.sub: work around command assignment bug in some shells

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When combining variable assignments with a shell command, some older
shells (notably heirloom-sh and presumably also Solaris 10 /bin/sh)
have a bug which causes the assignment to alter the current execution
environment whenever the command is a shell built-in.  For example:

  % dash -c 'x=good; x=bad echo >/dev/null; echo $x'
  good

  % jsh -c 'x=good; x=bad echo >/dev/null; echo $x'
  bad

The config.sub script contains a few commands of the form:

  IFS=- read ...

which triggers this bug, causing the IFS assignment to persist for the
remainder of the script.  This can cause misbehaviour in certain cases,
for example:

  % jsh config.sub i386-linux-gnu
  config.sub: test: unknown operator gnu

  % jsh config.sub i386-gnu/linux
  sed: can't read s|gnu/linux|gnu|: No such file or directory
  Invalid configuration `i386-gnu/linux': OS `' not recognized

* config.sub: Save and restore IFS explicitly to avoid shell bugs.
* doc/config.sub.1: Regenerate.

Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
This commit is contained in:
Nick Bowler 2021-08-14 12:20:38 -04:00 committed by Dmitry V. Levin
parent 2707e389a5
commit 191bcb948f
2 changed files with 8 additions and 2 deletions
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8
config.sub vendored
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@ -4,7 +4,7 @@
# shellcheck disable=SC2006,SC2268 # see below for rationale
timestamp='2021-08-04'
timestamp='2021-08-14'
# This file is free software; you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by
@ -121,9 +121,11 @@ esac
# Split fields of configuration type
# shellcheck disable=SC2162
saved_IFS=$IFS
IFS="-" read field1 field2 field3 field4 <<EOF
$1
EOF
IFS=$saved_IFS
# Separate into logical components for further validation
case $1 in
@ -935,9 +937,11 @@ case $basic_machine in
*-*)
# shellcheck disable=SC2162
saved_IFS=$IFS
IFS="-" read cpu vendor <<EOF
$basic_machine
EOF
IFS=$saved_IFS
;;
# We use `pc' rather than `unknown'
# because (1) that's what they normally are, and
@ -1317,9 +1321,11 @@ case $basic_os in
;;
*-*)
# shellcheck disable=SC2162
saved_IFS=$IFS
IFS="-" read kernel os <<EOF
$basic_os
EOF
IFS=$saved_IFS
;;
# Default OS when just kernel was specified
nto*)

2
doc/config.sub.1
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@ -1,5 +1,5 @@
.\" DO NOT MODIFY THIS FILE! It was generated by help2man 1.47.16.
.TH CONFIG.SUB "1" "August 2021" "GNU config.sub (2021-08-04)" "User Commands"
.TH CONFIG.SUB "1" "August 2021" "GNU config.sub (2021-08-14)" "User Commands"
.SH NAME
config.sub \- validate and canonicalize a configuration triplet
.SH SYNOPSIS